The invention relates to a lens tester for testing lenses and more particularly a lens tester which may easily test any number of desired points in the image plane a lens for the value of the transfer function at these points at all focal planes within the lens focal range and for any desired number of format positions in a focal plane to determine the one best focal plane in the focal range and the best format position in that focal plane.
Current interest in reproducing machinery such as xerography and photography has brought about a need for high resolution lenses to be used in such combinations and a method and apparatus for testing such lens. Previous lens testing systems have been developed; however, none of the previous testing systems have been able to test multiple points in a lens and multiple formats for the lens in the focal range of the lens.
The need has developed for a lens testing apparatus which may easily test any desired number of points in a lens image and determine the best focal plane in the focal range of the lens and the best format position in that focal plane of the lens during a single testing operation. This testing operation must be done quickly and efficiently since the combination of possible focal planes, points to be tested in the lens and format positions in each focal plane in the focal range of the lens is an extremely large number.